1. Field of the Invention
The present invention concerns a method and a device for an automatic determination of objects that attenuate high-energy (penetrating) radiation, by magnetic resonance. The invention also concerns a corresponding magnetic resonance apparatus and a computer-readable medium encoded with programming instructions for computerized implementation of such a method.
2. Description of the Prior Art
The article “Magnetic Resonance: An Introduction to Ultra-short TE (UTR) Imaging”, M. D. Robson et al., Comput Assist Tomogr., Vol. 27, No. 6, November/December 2003 describes the basic principles of magnetic resonance imaging.
In order to irradiate tumors, such as cancer tumors, with high-energy radiation, in particular gamma radiation, image data are required for the following reasons:                1. Based on the image data, a target volume (region of interest) is determined, which is to be irradiated.        2. Based on the image data, tissue can be localized that is sensitive to radiation, for example, nerves.        3. Based on the image data, any attenuation of the high-energy radiation in its propagation to the target volume is determined.        
According to the state of the art, MR image data, i.e., image data that has been prepared by a magnetic resonance tomography, is used for Points 1 and 2, but it is conventional to use 3D CT image data for Point 3. Since image data prepared by absorption of X-Rays are obtained using a computed tomography apparatus, intensity values of the CT scanners show the density of the objects represented in the CT images in good resolution (“Hounsfield units”), which is why computed tomography is well suited for the task described under Point 3. It should be pointed out that that it is also possible to use CT images for all three above-mentioned points, which is still quite common.
The preparation of CT images by computed tomography based on irradiation with X-rays represents a radiation stress for the person from whom the CT images are acquired. In addition, the development of increasingly accurate irradiation methods, which allow focus delimitation in the millimeter range and thus exhibit a modulation of an intensity distribution in the focus, and the absence of good soft-tissue contrast in the CT images, is increasingly perceived as a disadvantage. When both MT images and CT images are prepared, two relatively costly installations must be used (a computed tomography system and a magnetic resonance tomography system) in order to perform the task described in Points 1 to 3 above.